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721.
Water, Air, &; Soil Pollution: Focus - The mountain ecosystems of the Hindu Kush Himalayas are generally considered to be pristine despite little available data to confirm it. Is there any... 相似文献
722.
Gareth K. Phoenix Jonathan R. Leake David J. Read J. Philip Grime John A. Lee 《Water, Air, & Soil Pollution: Focus》2004,4(6):159-167
Semi-natural calcareous and acidic grasslands are known to be sensitive to increased atmospheric N deposition. However, the fate of pollutant N within these systems is unknown. This paper reports on the first studies to determine the fate of added N within a calcareous and an acidic grassland subject to long-term simulated enhanced N deposition. Intact soil/turf cores were removed from field plots treated for six years with enhanced N deposition (ambient +0, +35 and +140 kg N ha–1 year–1). Cores were inserted into lysimeters and output fluxes of N were monitored in detail. Complete N budgets—calculated from the N flux data—showed considerable accumulation of N within the treated grasslands, up to 76% and 38% of pollutant N in the calcareous and acidic grasslands respectively. In the second study, the short-term (21 day) fate of pollutant N was determined by tracing 15N labelled ammonium nitrate (+35 kg N ha–1 year–1) though the acidic and calcareous lysimeters into plant, soil and leachate pools. Up to 91% and 59% of 15N was recovered in soils and vegetation of the calcareous and acidic grasslands respectively, with negligible amounts recovered in soil extractable ammonium and nitrate (<0.3%) and in leachate (<0.02%). This rapid short-term immobilisation of pollutant N supports the long-term accumulation of the element calculated from the N flux study. 相似文献
723.
The Influence of Atmospheric N Deposition on Nitrous Oxide and Nitric Oxide Fluxes and Soil Ammonium and Nitrate Concentrations 总被引:2,自引:0,他引:2
U. Skiba C. Pitcairn L. Sheppard V. Kennedy D. Fowler 《Water, Air, & Soil Pollution: Focus》2004,4(6):37-43
The deposition of atmospheric N to soils provides sources of available N to the nitrifying and denitrifying microbial community and subsequently influences the rate of NO and N2O emissions from soil. We have investigated the influence of three different sources of enhanced N deposition on NO and N2O emissions 1) elevated NH3 deposition to woodlands downwind of poultry and pig farms, 2) increased wet cloud and occult N deposition to upland forest and moorland and 3) enhanced N deposition to trees as NO
3
–
and NH
4
+
aerosol. Flux measurements of NO and N2O were made using static chambers in the field or intact and repacked soil cores in the laboratory and determination of N2O by gas chromatography and of NO by chemiluminescence analysis. Rates of N deposition to our study sites were derived from modelled estimates of N deposition, NH3 concentrations measured by passive diffusion and inference from measurements of the 210Pb inventory of soils under tree canopies compared with open grassland. NO and N2O emissions and KCl-extractable soil NH
4
+
and NO
3
–
concentrations all increased with increasing N deposition rate. The extent of increase did not appear to be influenced by the chemical form of the N deposited. Systems dominated by dry-deposited NH3 downwind of intensive livestock farms or wet-deposited NH
4
+
and NO
3
–
in the upland regions of Britain resulted in approximately the same linear response. Emissions of NO and N2O from these soils increased with both N deposition and KCl extractable NH
4
+
, but the relationship between NH
4
+
and N deposition (ln NH
4
+
= 0.62 ln Ndeposition + 0.21, r
2 = 0.33, n = 43) was more robust than the relationship between N deposition and soil NO and N2O fluxes. 相似文献
724.
Helen Briassoulis 《Environmental management》1987,11(2):271-278
Acid deposition is a muitifaceted environmental phenomenon whose control represents one of the most controversial environmental policy areas. Because of the longrange transport of air pollutants contributing to acid deposition, its control is the responsibility of more than one region. Given the interdependence between the economic and environmental impacts of acid deposition as well as the interregional conflicts over its control, the present article proposes an interregional integrated economic-environmental model for the study of the impacts of acid deposition control policies. This model is solved with the use of a compromise programming procedure which facilitates the explicit treatment of conflicting regional goals. After the theoretical and operational forms and the solution procedure of the proposed model are described, the use of the model is illustrated with a simulation example using the 1963 MRIO accounts and hypothetical environmental data. The compromise programming procedure can form the basis for interactive decision processes when policy makers are exposed to the solutions yielded by the model. The model's usefulness and future research directions are discussed. 相似文献
725.
Charles P. Newcombe 《Environmental management》1985,9(4):277-288
The problem of acid deposition and its harmful effects on aquatic ecosystems has created a new branch of science that is called upon to provide the knowledge on which legislative controls can be based. However, because of the nature of existing legislation, which requires evidence of cause and effect between industrial emissions and pollution, and because of science's inability to provide this information over the short term, considerable controversy has arisen about whether sufficient information exists to warrant control measures at this time. Among those who advocate controls, there is genuine divergence of opinion about how stringent the controls must be to achieve any desired level of protection.The controversy has led to an impasse between the scientific and political participants, which is reflected in the slow pace of progress toward an effective management strategy. Resolution of the impasse, at least in the short term, may demand that science and politics rely on empirical models rather than explanatory ones. The empirical model, which is the major proposal in this article, integrates all of the major variables and many of the minor ones, and constructs a three-dimensionally curved surface capable of representing the status of any waterbody subjected to the effects of acid deposition. When suitably calibrated—a process involving the integration of knowledge and data from aquatic biology, geochemistry, meteorology, and limnology—it can be used to depict limits to the rate of acid deposition required for any level of environmental protection. Because it can generate a pictorial display of the effects of management decisions and legislative controls, the model might serve as a basis for enhancing the quality of communication among all the scientific and political participants and help to resolve many of their controversies. 相似文献
726.
Steven R. Abt James F. Ruff Cesar Mendoza 《Journal of the American Water Resources Association》1983,19(4):571-576
ABSTRACT One component of the local scour process near a culvert outlet is the formation of an aggraded mound downstream of the scour area. This investigation presents a series of observations and empirical relationships depicting the formation, growth, and estimated maximum dimensions of a mound in a uniformly graded sand material due to clear water scour. The maximum dimensions of the mound were correlated to the discharge intensity (Qg-0.5 D-2.5), the maximum dimensions of the scour hole, time, and tailwater elevation. The concept of an approximate area of scour influence was developed relating the mound width, scour hole length, and mound length as a function of the culvert diameter and discharge intensity. 相似文献
727.
The atmospheric deposition of reactive nitrogen on turf grassland in Tsukuba, central Japan, was investigated from July 2003
to December 2004. The target components were ammonium, nitrate, and nitrite ions for wet deposition and gaseous ammonia, nitric
and nitrous acids, and particulate ammonium, nitrate, and nitrite for dry deposition. Organic nitrogen was also evaluated
by subtracting the amount of inorganic nitrogen from total nitrogen. A wet-only sampler and filter holders were used to collect
precipitation and the atmospheric components, respectively. An inferential method was applied to calculate the dry deposition
velocity of gases and particles, which involved the effects of surface wetness and ammonia volatilization through stomata
on the dry deposition velocity. The mean fraction of the monthly wet to total deposition was different among chemical species;
37, 77, and 1% for ammoniacal, nitrate-, and nitrite-nitrogen, respectively. The annual deposition of inorganic nitrogen in
2004 was 47 and 48 mmol m−2 yr−1 for wet and dry deposition, respectively; 51% of atmospheric deposition was contributed by dry deposition. The annual wet
deposition in 2004 was 20, 27, and 0.07 mmol m−2 yr−1, and the annual dry deposition in 2004 was 35, 7.4, and 5.4 mmol m−2 yr−1 for ammoniacal, nitrate-, and nitrite-nitrogen, respectively. Ammoniacal nitrogen was the most important reactive nitrogen
because of its remarkable contribution to both wet and dry deposition. The median ratio of the organic nitrogen concentration
to total nitrogen was 9.8, 17, and 15% for precipitation, gases, and particles, respectively. 相似文献
728.
Lignite mining and processing has caused a pronounced impact both directly and indirectly on soils and ecosystems across large
areas of the former GDR. We studied soils of pine forest ecosystems at sites affected by severe alkaline dust and sulphur
deposition, stemming from lignite fired power plant emission, and at dumped sites from lignite mining. In this paper we summarize
our main results and evaluate the long-term impact of lignite mining and combustion on the environment.
The pine ecosystems on naturally developed soils show a clear effect of deposition history along a former deposition gradient
with distinct changes in chemical properties of organic surface layers and mineral soil as well as in element turnover and
cycling rates.
Afforested sites on mining dumps are directly affected by the composition of the dumped substrates. Over a large area (800
km2) these substrates are dominated by Tertiary sediments with varying amounts of lignitic particles and pyrite that result in
phytotoxic site conditions (pH < 3, high salt and metal contents). High amelioration doses of liming material (up to 200 t
ha−1) were applied for restoration purposes. We studied the development of these sites over a period of 60 years using a false-time
series approach. Beside the extreme soil conditions, element budgets of these sites are characterized by very high element
release rates over decades caused by pyrite oxidation and primary mineral weathering. 相似文献
729.
An in situ erosion flume was used to measure the stability of sediment deposits in Hamilton Harbour, Ontario, Canada. The flume consists
of a rectangular duct with an opening at the bottom. A submerged pump attached to the downstream end of the flume circulates
the ambient water through the flume, thereby generating turbulent shear flows inside the flume. When the flume rests on a
sediment deposit, the exposed part of the sediment deposit is subjected to the flow shear stress. By applying a continually
increasing flow shear stress on the sediment deposit and by measuring the amount of sediment erosion, it is possible to assess
the erosional stability of the sediment deposits. An under water video camera was mounted on the flume to get visual images
of the sediment erosion process. The flume was used at two sites in the Harbour. The erosional resistances measured by the
flume for the two sites were different. Measurement of dry density of the sediment deposits using an ultrasonic device was
carried out to explain the differences in the stability of sediment deposits from the two sites. 相似文献
730.
Ecophysiological responses of winter wheat seedling to aerosol
wet deposition of Xi’an area, China 总被引:1,自引:0,他引:1
Yiping Chen 《环境科学学报(英文版)》2010,22(11):1786-1791
Aerosol leads to 30% reduction in solar radiation reaching the earth’s surface, and a similar reduction in crops yield for both wheat
and rice. To determine the effect of aerosol wet deposition on crops, aerosol samples were collected in September, 2006 at Xi’an
urban suburb (34?44 N, 109?49 E), and wheat seedlings were treated with aerosol of different concentrations in laboratory conditions.
Changes in physiological and biochemical parameters of wheat seedlings were measured. In comparison with the control, the activities
of superoxide dismudase (SOD) and catalase (CAT) and the concentration malondialdehyde (MDA) and oxidized glutathione (GSSG)
of wheat seedlings increased progressively with increasing concentrations of added aerosol, while the opposite trend was seen for the
activities of nitric oxide synthase (NOS), the concentrations of glutathione (GSH) and nitric oxide (NO), and the ratio of GSH/GSSG.
When the seedlings were treated with the aerosol of 1 and 2 mg/L, the coleoptile elongation, shoot elongation and biomass accumulation
were increased, the effect at treatment of 2 mg/L was most significant. However, aerosol treatments with rates of 3 and 4 mg/L resulted
in a decrease in coleoptile elongation, shoot elongation and biomass accumulation in seedlings, and significant effect was for the
treatment of 4 mg/L. Hence, lower concentrations of aerosol wet deposition were in favor of crops growth, but its higher concentrations
could result in deleterious effects for crops and decreased crops growth. 相似文献